JPH09223831A - Piezoelectric thin film, and its manufacture and ink jet recording head using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the characteristics of the piezoelectric strain and permittivity. etc., of a piezoelectric material thin film, by making the values of its film thickness and the average grain size of its crystal grains specific, and by eliminating any laminar discontinuous surface in its section. SOLUTION: After forming a platinum electrode 12 on a silicon substrate 11 to apply a sol thereto, burning the resultant matter temporarily at 400 deg.C a porous gel thin film 13 of 0.3μm in film thickness is formed. Further, repeating two times the applications and temporary burnings of the sols, a new porous gel thin film 13 of 0.9μm in film thickness is formed. Heating this film 13 in the oxygen atmosphere of an RTA furnace, a minute thin film 14 of 0.6μm in film thickness is obtained. Further thereon, repeating three times the applications and temporary burnings of the sols, a new porous gel thin film 13 of 0.9μm in film thickness is obtained. Then, pre-annealing this film 13 in the RTA furnace, a new thin film 14 having a minute crystalline and a film thickness of 1.2μm is obtained. After peeling a resist from this film 14, annealing this resultant substrate 11 at 900 deg.C in the RTA furnace, a piezoelectric material thin film 15 of 1.2μm in film thickness is obtained. From the observation of the section of this film 15 by an SEM, a thin-film configuration with an average grain size of 0.03μm and no laminar discontinuous surface is obtained. Whenever the piezoelectric thin film 15 with a film thickness not smaller than 0.5μm and not larger than 20μm and an average grain size not smaller than 0.005μm and not larger than 0.2μm is manufactured by this method, its favorable characteristic can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric thin film used as an actuator in an inkjet recording device or the like.

[0002] lead zirconate titanate piezoelectric represented by (hereinafter sometimes referred to as "PZT"), ferroelectric thin film, a sputtering method, a sol-gel method, CVD method, produced by the laser ablation method or the like can do.

Particularly, the sol-gel method is excellent in composition controllability. Further, there is an advantage that a thin film can be easily formed by repeating the application of the sol composition and the firing thereof. Furthermore, patterning using a photo-etching process is possible, and as a result, it can be easily formed into an element. An ink jet recording head using a piezoelectric thin film manufactured by the sol-gel method has also been proposed (Japanese Patent Publication No. 5-504740). When used as a piezoelectric element of an inkjet recording head, it is generally said that a film thickness of about 0.5 μm to 20 μm is required. Further, the piezoelectric element of the ink jet recording head has a high piezoelectric strain constant, and it is said that it is necessary to grow crystal grains by annealing at a temperature of 700 ° C. or higher in order to obtain such a high piezoelectric strain constant. .

However, when a piezoelectric thin film having a certain film thickness, for example, a film thickness of 1 μm or more, is to be manufactured by the sol-gel method, cracks may occur in the film during the annealing process for obtaining the perovskite structure. Was observed.

In addition, there has been proposed a method for increasing the film thickness by firing at a high temperature to crystallize the composition for applying a sol or gel composition, and repeating this to increase the film thickness (for example, Ph.
i1ips J. Res. 47 (1993) 263-2
85). However, as far as the inventors know, the piezoelectric thin film obtained by this method has a layered laminated interface. Such a laminated interface is not preferable for piezoelectric characteristics, and good patterning may not be possible in etching for device formation.

Therefore, it can be said that there is a need for a piezoelectric thin film having good characteristics and a method for manufacturing the same.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a piezoelectric thin film having good characteristics, for example, a high dielectric constant and a high piezoelectric strain constant, and a method for producing the same.

Another object of the present invention is to provide a piezoelectric thin film which does not cause cracks during annealing and has no laminated interface, and a method for manufacturing the same.

The present inventors have now found a thin film piezoelectric material having good characteristics. Further, they have found a piezoelectric composition extremely advantageous for a piezoelectric in the form of a thin film and a method for manufacturing a piezoelectric thin film suitable for manufacturing the same. The present invention is based on this finding.

Therefore, the piezoelectric thin film according to the present invention is a piezoelectric thin film having a thickness of 0.5 μm or more and 20 μm or less, and the thin film is composed of crystal grains having an average grain size of 0.005 μm or more and 0.2 μm or less, and It does not have a layered discontinuous surface in the cross section of the thin film.

According to the present invention, there is provided a piezoelectric thin film having a specific composition, wherein the piezoelectric thin film according to the first aspect is xPb (M
g _1/3 Nb _2/3 ) O ₃ -yPbZrO ₃ -zPbTiO
_In the ternary composition diagram as shown in FIG. 1, which is composed of a ternary piezoelectric material represented by 3, the following A, B,
It has a composition within the range of four points of C and D.

A (x = 0.05, y = 0.40, z = 0.55) B (x = 0.05, y = 0.60, z = 0.35) C (x = 0.25 , Y = 0.30, z = 0.45) D (x = 0.25, y = 0.50, z = 0.25) Further, according to the present invention, a piezoelectric thin film having another specific composition is provided. The piezoelectric thin film according to the second aspect is Pb (1-
α) Γα [(Mg _1/3 Nb _2/3 ) xZryTiz] O ₃
(Where x, y, and z are molar ratios, and x + y + z = 1
And x, y, and z are within the following four points A, B, C, and D in the ternary composition diagram of this formula, A (x = 0.05, y = 0.40, z = 0.55), B (x = 0.05, y = 0.60, z = 0.35), C (x = 0.25, y = 0.30, z = 0.45), D (x = 0.25, y = 0.50, z = 0.25), and Γ in the above formula is Sr, Ca, Ba, Bi, or L.
represents any element of a, and α in the above formula is 0 <α
It is an arbitrary number that satisfies the relation of ≦ 0.2.

The method for producing a piezoelectric thin film according to the first aspect of the present invention is a method for producing a piezoelectric thin film by a sol-gel method, which comprises: a) a sol of a metal component constituting the piezoelectric film, and A step of applying a sol composition containing a molecular compound on a substrate and drying it to form a film; and b) baking the obtained film to contain an amorphous metal oxide. A calcination step of forming a porous gel thin film, c) a pre-annealing step of annealing the obtained porous gel thin film to form a film made of a crystalline metal oxide, d) the above step a) , B), and c) are repeated at least once to form a laminated film of crystalline metal oxide, and e) the film obtained in step d) is annealed to obtain a perovskite-type film in the film. And a step of growing large crystal grains of

The method for producing a piezoelectric thin film according to the second aspect of the present invention is a method for producing a piezoelectric thin film by a sol-gel method, which comprises: a) a sol of a metal component constituting the piezoelectric film, and A step of applying a sol composition containing a molecular compound on a substrate and drying it to form a film; and b) baking the obtained film to contain an amorphous metal oxide. A calcination step of forming a porous gel thin film, and f) a step of repeating the above steps a) and b) at least once to form a laminated film of porous thin films containing an amorphous metal oxide. , C ′) a pre-annealing step of annealing the laminated film to form a film made of a crystalline metal oxide, and d ′) the above steps f) and c ′) are repeated at least one or more times to obtain a crystal. Forming a laminated film of films made of high quality metal oxide, and e ') The step of annealing the film obtained in step d ′) to grow the perovskite type crystal grains in the film to a large extent.

[0015]

DETAILED DESCRIPTION OF THE INVENTION Piezoelectric Thin Film The piezoelectric thin film according to the present invention has a thickness in the range of 0.5 μm or more and 20 μm or less. The piezoelectric thin film according to the present invention has preferable characteristics in such an extremely thin form. In order to obtain this preferable characteristic, it is preferable that the thin film is made of crystal grains having an average grain size of 0.005 μm or more and 0.2 μm or less and does not have a layered discontinuous surface in the thin film cross section. According to a preferred embodiment of the present invention, the thickness of the thin film is more preferably 0.7 μm or more and 10 μm or more.
The average grain size of the crystal grains is 0.01 μm or more and 0.1 μm or less. Further, in the present invention, those in which the perovskite type is the main one are preferable. Such a piezoelectric thin film has good characteristics. Specifically, the relative dielectric constant is about 1,000 to 3,500, more preferably about 1,200 to 2,800. Further, the piezoelectric strain constant is 70 pC / N or more, more preferably 100 pC
/ N or more.

The above-mentioned piezoelectric thin film has more preferable properties when combined with the specific composition according to the present invention described below.

According to a preferred embodiment of the present invention, the piezoelectric thin film according to the present invention is xPb (Mg _1/3 Nb _2/3 ) O ₃ -y.
In the ternary composition diagram as shown in FIG. 1, which consists of a ternary piezoelectric material represented by PbZrO ₃ -zPbTiO ₃ , the following four points A, B, C, and D are within the range: It has a composition.

A (x = 0.05, y = 0.40, z = 0.55) B (x = 0.05, y = 0.60, z = 0.35) C (x = 0.25 , Y = 0.30, z = 0.45) D (x = 0.25, y = 0.50, z = 0.25) A piezoelectric thin film having a composition according to the first aspect of the present invention is
It is made of a ternary piezoelectric material represented by the above formula and has a composition within the region shown in FIG.

In the piezoelectric thin film having the composition according to the second aspect of the present invention, Pb in the above formula is up to about 20 mol%, preferably 5 to 15 mol%, Sr, C.
It may have a composition substituted by an element selected from a, Ba, Bi, and La. That is, Pb
(1-α) Γα [(Mg _1/3 Nb _2/3 ) xZryTi
z] O ₃ (where x, y, and z are molar ratios, and x + y
+ Z = 1), and x, y, and z are within the range of the following four points A, B, C, and D in the ternary composition diagram of this formula, A (x = 0 .05, y = 0.40, z = 0.55), B (x = 0.05, y = 0.60, z = 0.35), C (x = 0.25, y = 0.30) , Z = 0.45), D (x = 0.25, y = 0.50, z = 0.25), and Γ in the above formula is Sr, Ca, Ba, Bi, or L.
represents any element of a, and α in the above formula is 0 <α
It is represented by an arbitrary number satisfying the relation of ≦ 0.2. With such a composition, a piezoelectric thin film having improved characteristics can be obtained.

According to another preferred embodiment of the present invention, in the above formula, some or all of Mg is Co,
It is substituted by an element selected from Zn, Mn, and Ni, a part of Nb is replaced by Ta or Sb, or a part of Zr or Ti is Sb,
Provided is a piezoelectric thin film which is substituted with an element selected from Fe, Al, and Cr or is modified in one or more compositions. By modifying the composition as described above, it becomes possible to easily control the piezoelectric strain constant, the relative dielectric constant, and the Young's modulus to appropriate values. Particularly, the control of the relative permittivity is preferable from the viewpoint of controlling the heat generation amount of the piezoelectric thin film.

According to a preferred embodiment of the present invention, Pb or a Pb compound (eg PbO) is added to Pb: (Mg + N
There is provided a piezoelectric thin film having a composition further containing b + Zr + Ti) in a molar ratio range of 1 to 1.2: 1.
A more preferred molar ratio is 1-1.15: 1. Such a piezoelectric thin film having an excessive Pb component is preferable because it has a large piezoelectric strain constant.

A voltage V (V = V) whose electric field depends on time is applied to a piezoelectric thin film element having a capacitance C, that is, a capacitor.
When (t): t is time, the current i flowing through the piezoelectric thin film element is i = C (dV / dt). Since the heat generation amount Q generated in the piezoelectric thin film element at this time is proportional to i × i, it is important to reduce the capacitance C, in other words, to suppress the relative dielectric constant of the piezoelectric thin film.

On the other hand, the amount of strain applied to the piezoelectric thin film when a voltage is applied is proportional to the applied voltage. Even if the decrease of the piezoelectric strain characteristic is compensated by the increase of the applied voltage, if the time gradient of the voltage V is kept constant from the relation of i = C (dV / dt), the adverse effect of heat generation can be reduced.

Controlling the Young's modulus is advantageous for the following reasons. That is, in the ink jet recording head that ejects ink droplets by the pressure generated in the ink flow path, the rigidity of the generation portion or the transmission portion of the generated pressure, in other words, the elastic compliance (1 / Y) of the constituent members is important. It becomes a characteristic factor of ink ejection. The elastic compliance of the constituent members becomes factors such as the speed and weight of ejected ink droplets, damping of ink vibrations in the flow channels that influence the response frequency, and interference between adjacent ink flow channels.

In the ink jet recording head using the piezoelectric thin film element according to the present invention, it is possible to easily suppress the Young's modulus of the piezoelectric thin film attached to the vibrating plate forming the ink flow path, and to make the compliance of the ink flow path. It is effective to increase the ink ejection characteristics, especially to prevent interference between adjacent ink flow paths.

The composition of the piezoelectric thin film according to the present invention can be controlled by controlling the metal composition in the sol composition used in the production method described later.

Manufacturing Method of Piezoelectric Thin Film Sputtering Method As a preferable thin film manufacturing method, sputtering can be mentioned. That is, using a PZT sintered body of a specific component as a sputtering target, an amorphous piezoelectric film precursor film is formed on the electrode film by sputtering.

The following amorphous precursor is heated to be crystallized and sintered. This heating is preferably performed in an oxygen atmosphere (for example, in oxygen or in a mixed gas of oxygen and an inert gas such as argon). In the heating step, the precursor film is preferably 500 to 70 in an oxygen atmosphere.
Heat at a temperature of 0 ° C. The precursor film is crystallized by heating, and the crystal grain size is 0.005 μm or more and 0.2 μm or more.
It is implemented so that it may become the following ranges.

The piezoelectric thin film according to the present invention can be preferably manufactured by the following two modified sol-gel methods.

Manufacturing method step by sol-gel method according to the first aspect a) The manufacturing method of the piezoelectric film according to the present invention is based on the sol-gel method. That is, a hydrated complex of a metal component hydroxide capable of forming a piezoelectric film, that is, a sol, is dehydrated into a gel, and the gel is heated and baked to prepare an inorganic oxide, that is, a piezoelectric film. Based on method.

In the present invention, the sol of the metal component forming the piezoelectric film can be prepared by hydrolyzing a metal alkoxide or acetate capable of forming the piezoelectric film with, for example, an acid. In the present invention, the composition of the piezoelectric thin film described above can be obtained by controlling the composition of the metal in the sol. That is, titanium, zirconium, lead,
Further, each alkoxide or acetate of another metal component is used as a starting material. The present invention has the advantage that the composition of the metal components forming the piezoelectric thin film is substantially maintained until the piezoelectric thin film is finally formed. That is, during the firing and annealing treatment, there is very little variation due to evaporation of metal components, especially lead components, and therefore the composition of the metal components in these starting materials should match the metal composition in the final piezoelectric thin film. Become. In other words, the composition of the sol is determined according to the piezoelectric film to be produced.

Further, according to a preferred embodiment of the present invention, in order to obtain the above-mentioned piezoelectric thin film in which the Pb component is excessive, the lead component in the sol is up to 20 mol% than the amount required from the stoichiometry. It is preferable that the amount is in excess, preferably up to 15 mol%.

In the present invention, this sol is preferably used as a composition mixed with an organic polymer compound. This organic polymer compound absorbs the residual stress of the thin film during drying and firing, and effectively prevents the thin film from cracking. Specifically, when a gel containing this organic polymer is used, pores are generated in the gelled thin film described later. It is considered that these pores absorb the residual stress of the thin film in the pre-annealing and annealing steps which will be described later. Here, as the organic polymer compound preferably used, polyvinyl acetate, hydroxypropyl cellulose, polyethylene glycol, polyethylene glycol monomethyl ether, polypropylene glycol, polyvinyl alcohol, polyacrylic acid, polyamide, polyamic acid, acetyl cellulose and derivatives thereof, And copolymers thereof. In addition,
According to a preferred embodiment of the present invention, by adding polyvinyl acetate, a porous gel thin film having a large number of pores of about 0.05 μm, and by adding hydroxypropyl cellulose, a size of 1 μm or less and a wide distribution can be obtained. It is possible to form a porous gel thin film having

According to a preferred embodiment of the present invention, polyethylene glycol having an average molecular weight of about 285 to 420 is preferable. Further, polypropylene glycol having an average molecular weight of about 300 to 800 is preferable.

In the manufacturing method according to the present invention, first, this sol composition is applied to the substrate on which the piezoelectric thin film is to be formed. Here, the substrate means a substrate on which the piezoelectric thin film element is to be finally formed. Therefore, for example, when an inkjet recording head is to be manufactured using the piezoelectric thin film according to the present invention as described below, a substrate is one in which a thin film electrode is provided on a crystalline silicon substrate.

The coating method is not particularly limited, and may be a commonly used method such as spin coating, dip coating, roll coating or bar coating. It is also possible to apply by flexographic printing, screen printing, offset printing or the like.

According to a preferred embodiment of the present invention, the thickness of the film formed by coating is 0.01 μm when the thickness of the porous gel thin film formed in step b) described below is taken into consideration, considering the following steps. The above control is preferable, and the control is more preferably about 0.1 to 1 μm.

After coating, the film is dried. Drying may be performed by natural drying or by heating to a temperature of 200 ° C. or lower.

According to a preferred embodiment of the present invention, the film can be thickened by further coating the film on the dried film. In this embodiment, the base film is preferably dried at a temperature of 80 ° C. or higher.

Step b) : In this step, the film of the sol composition obtained in the above step a) is gelled. That is, the film obtained in step a) is baked to obtain a porous gel thin film made of an amorphous metal oxide substantially free of residual organic substances. This step may be referred to as a calcination step in this specification.

The calcination may be carried out by heating the sol composition film at a temperature sufficient for gelling and removing organic substances from the film for a sufficient time. According to a preferred embodiment of the present invention, the firing temperature is preferably in the range of 300 to 450 ° C, more preferably 350 to 400 ° C. The firing time varies depending on the temperature and the type of furnace used, but when a degreasing furnace is used, for example, 10 to 1
It is preferably about 20 minutes, more preferably about 15 to 60 minutes, and when using a hot plate, 1 to 60 minutes.
It is preferably about 5 minutes, more preferably about 5 to 30 minutes.

By the above steps a) and b), FIG.
As shown in (1), the porous gel thin film 13 is formed on the electrode 12 provided on the substrate 11.

Step c) A step of heating and burning the porous gel thin film obtained in the above step b) to convert it into a film made of a crystalline metal oxide. This process may be called a pre-annealing process in this specification.

The calcination may be carried out by heating the porous gel thin film at a temperature necessary for converting it into a film made of a crystalline metal oxide. However, this firing does not have to be performed until the perovskite type crystals occupy most of the crystals. Firing may be terminated when the gel film has crystallized homogeneously. According to a preferred embodiment of the present invention, the firing temperature is preferably 400 to 800 ° C, more preferably 550 to 750 ° C. The firing time varies depending on the temperature and the type of furnace used, but when an annealing furnace is used, for example, it is preferably about 0.1 to 5 hours, more preferably about 0.5 to 2 hours, and R
TA (Rapid Thermal Annealin
g) When using a furnace, it is preferably about 0.1 to 10 minutes,
It is more preferably about 1 to 5 minutes.

Further, according to a preferred embodiment of the present invention, it is preferable that the pre-annealing is carried out in two steps.
Specifically, it is preferable to perform the first step at a temperature in the range of 400 ° C to 600 ° C and the second step at a temperature in the range of 600 ° C to 800 ° C or less. According to a more preferred embodiment, the first stage is carried out at a temperature of 450 to 550 ° C and the second stage is carried out at a temperature of 600 to 750 ° C.

By this step c), as shown in FIG. 2B, the porous gel thin film 13 is converted into the film 14 made of crystalline metal oxide.

Step d) In the present invention, the above steps a), b) and c) are repeated at least once to laminate a crystalline metal oxide film. Film thickness in repeated steps a), b), and c),
The calcination temperature and the pre-annealing conditions may be the same as in the case of forming the first film on the substrate.

The film thickness of the laminated film obtained as a result of this step may be appropriately determined in consideration of the film thickness of the final piezoelectric thin film, but is a film thickness such that cracks and the like do not occur in the next step e). It goes without saying that it is preferable.

The process d) is schematically shown in FIG.
As shown in (3), a new porous gel thin film 13 is formed on the previously formed film 14, and as a result of the subsequent pre-annealing, as shown in FIG. The thin film 13 is a film which is substantially integrated with the previously formed film 14. Here, the substantially integrated film means not only the case where there is no discontinuous layer between the laminated layers but also the discontinuous layer between the laminated layers, unlike the case of the final piezoelectric thin film according to the present invention. There may be. Then, if the steps a), b), and c) are further repeated, as shown in FIG.
, A new porous gel thin film 13 is formed,
As a result of the subsequent pre-annealing, as shown in FIG. 2 (6), this film 13 becomes a film substantially integrated with the crystalline laminated film 14.

The patterning for forming the piezoelectric thin film element and the formation of the upper electrode are preferably performed on the thin film at this stage.

Step e) This step is a step of further firing the laminated film of the film made of the crystalline metal oxide obtained as described above to grow a perovskite type crystal. This step may be referred to as an annealing step in this specification.

According to a preferred embodiment of the present invention, the firing temperature is preferably in the range of 600 to 1200 ° C, more preferably 800 to 1000 ° C. Although the firing time varies depending on the temperature and the type of furnace used, for example, when an annealing furnace is used, it is preferably about 0.1 to 5 hours, more preferably about 0.5 to 2 hours. When used, it is preferably about 0.1 to 10 minutes, more preferably about 0.5 to 3 minutes.

Further, according to a preferred embodiment of the present invention, it is preferable to carry out the annealing in two steps. Specifically, it is preferable that the first step be performed at a temperature in the range of 600 ° C to 800 ° C and the second step be performed at a temperature in the range of 800 ° C to 1000 ° C. According to a more preferred embodiment, the first stage is carried out at a temperature of 600 to 750 ° C and the second stage is carried out at a temperature of 800 to 950 ° C.

By the above operation, a piezoelectric thin film having no layered discontinuous layer in the thin film cross section can be manufactured.

According to a preferred embodiment of the present invention, crystal grains are grown by this annealing step, and a piezoelectric thin film having an average grain size of 0.005 μm or more and 0.2 μm or less can be obtained.

The piezoelectric thin film element shown in FIG. 2 (7) is
This is an example in which the electrode 12 is further provided on the piezoelectric thin film 15 having no discontinuous layer obtained by this step.

Manufacturing method steps a) and b) by the sol-gel method according to the second aspect The steps a) and b) in the method for manufacturing a piezoelectric film according to the second aspect of the present invention are the piezoelectric method according to the first aspect of the present invention. This is the same as steps a) and b) in the method for manufacturing a body thin film.

As a result of this step, a substrate 11 having an electrode 12 and a porous gel thin film 13 as shown in FIG. 3A is obtained.

Step f) In the method for producing a piezoelectric thin film according to the second aspect of the present invention, steps a) and b) are repeated at least once to form a laminated film of porous gel thin films. The film thickness and the calcination temperature in the above-described steps a) and b) may be the same as in the case where the film is formed the first time on the substrate.

According to a preferred embodiment of the present invention, the thickness of the laminated film is preferably 1 μm or less, more preferably 0.5 μm.
m or less. When the film thickness of the laminated film is about this level, the pre-annealing in the next step c ′) can be efficiently performed without the occurrence of cracks or the like.

As a result of this step, a laminated film in which a plurality of porous gel thin films 13 are laminated as shown in FIG. 3B is formed.

Step c ') This step is a step of firing the laminated film of the porous gel thin film obtained in the above step f) to convert it into a film made of a crystalline metal oxide. Similar to step c) in the method according to the first aspect.
In this specification, this step may also be referred to as a pre-annealing step.

The firing may be carried out by heating the laminated film of porous gel thin films to a temperature necessary for converting it into a film made of a crystalline metal oxide. However, this firing does not have to be performed until the perovskite type crystals occupy most of the crystals. Firing may be terminated when the gel film has crystallized homogeneously. The calcination temperature and time may be similar to step c) in the method according to the first aspect. Also, it may be carried out in two steps, similar to step c) in the method according to the first aspect.

As a result of this step, as shown in FIG. 3C, the laminated film of the porous gel thin film 13 is a crystalline thin film 14.
Is converted to

Step d ') In the method according to the second aspect of the present invention, the above steps f) and c') are repeated at least once or more. That is, a step of repeating the above steps a) and b) at least once to form a laminated film of a porous gel thin film, and firing the laminated film to convert it into a film made of a crystalline metal oxide, Repeat at least once more. Then, a laminated film of films made of crystalline metal oxide is formed.

Various conditions in the repeated steps a) and b) and step c ') may be the same as those described above.

The film thickness of the laminated film obtained as a result of this step may be appropriately determined in consideration of the film thickness of the final piezoelectric thin film, but the film thickness is such that cracks and the like do not occur in the next step e '). It goes without saying that it is preferable to have it.

As a result of this step, a new laminated film of the porous gel thin film 13 is formed on the previously formed film 14 as shown in FIG. ), A new porous gel thin film 1
The laminated film of No. 3 is a film substantially integrated with the film 14 formed previously. Here, the substantially integrated film means
It is synonymous with the above.

The patterning for forming the piezoelectric thin film element and the formation of the upper electrode are preferably performed on the thin film at this stage. FIG. 3 (6) shows the film 14 patterned into a desired shape.

Step e ') This step is a step of further firing the laminated film of the film made of the crystalline metal oxide obtained as described above to grow a perovskite type crystal.
Step e) similar to step e) in the method according to the first aspect. In this specification, this step may also be referred to as an annealing step.

The firing temperature and time may be about the same as step e) in the method according to the first aspect. Also, it may be carried out in two steps, similar to step e) in the method according to the first aspect.

The piezoelectric thin film element shown in FIG. 3 (7) is
This is an example in which the electrode 12 is further provided on the piezoelectric thin film 15 having no discontinuous layer obtained by this step.

Applications of piezoelectric thin film / Inkjet recording
The piezoelectric thin film according to the present invention may be used for various applications by utilizing its good characteristics.

For example, it can be used as a vibrator of an ink jet recording head. By using the piezoelectric thin film element according to the present invention, there are advantages that ink can be ejected with a large pressure and that driving can be performed at a high frequency.

A preferred specific example of the recording head using the piezoelectric thin film according to the present invention is as shown in FIG.
This recording head is configured by joining a single crystal Si substrate 21 provided with an ink sump 27 and a second substrate 26. A vibration plate 22, a lower electrode 23, a piezoelectric film 24, and an upper electrode 25 are formed on the single crystal Si substrate 21.

Ink is supplied to the ink reservoir 27 through an ink flow path (not shown). Here, when a voltage is applied to the piezoelectric film 24 through the lower electrode 23 and the upper electrode 25, the ink reservoir 27 is deformed and pressure is applied to the ink. By this pressure, ink is ejected from a nozzle (not shown), and inkjet recording can be performed.

Such an ink jet recording head can be manufactured according to a commonly used method.

[0078]

Example A1 Lead acetate (0.105 mol), zirconium acetylacetonate (0.045 mol), and magnesium acetate (0.005)
Mol and were dissolved in 30 ml of acetic acid by heating to 100 ° C. After cooling to room temperature, 0.040 mol of titanium tetraisopropoxide and 0.010 of pentaethoxyniobium
Mol and were added to and dissolved in 50 ml of ethyl cellosolve. After stabilizing by adding 30 ml of acetylacetone, polyethylene glycol # 400 (manufactured by Kanto Chemical Co.,
The average molecular weight of 380 to 420) was added at a ratio of 30% by weight with respect to the metal oxide in the sol, and well stirred to form a homogeneous sol.

A platinum electrode was formed on a silicon substrate by sputtering, and the sol was applied thereon by spin coating.
It was calcined at 00 ° C. As a result, an amorphous porous gel thin film having a thickness of 0.3 μm could be formed without cracks. Further, application of sol and calcination at 400 ° C. were repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Next, this thin film was placed in an oxygen atmosphere using an RTA furnace for 5
It was heated to 650 ° C. for 2 seconds, held for 1 minute, and pre-annealed to form a dense thin film having a thickness of 0.6 μm.

When the thin film was examined by X-ray analysis, a pyrochlore type crystal peak was detected. In addition, reflective FT-IR (Fourier transform infrared absorption spectrum analysis)
As a result of the examination, the absorption due to the hydroxyl group around 3400 cm ^-1 was not detected.

The process of applying the sol prepared above by spin coating to the thin film thus obtained and pre-baking at 400 ° C. was repeated three times to obtain an amorphous porous gel having a thickness of 0.9 μm. A thin laminated film was obtained. Next, it was pre-annealed by holding it at 650 ° C. for 1 minute using an RTA furnace to obtain a crystalline dense film having a thickness of 1.2 μm.

The obtained substrate was patterned using a photoresist and etched with borofluoric acid. After removing the resist, the substrate was annealed by holding it at 900 ° C. for 1 minute in an oxygen atmosphere using an RTA furnace. 1.2
A piezoelectric thin film having a thickness equal to the μm thickness was obtained. When the piezoelectric thin film was examined by X-ray analysis, a sharp and strong peak of perovskite type crystal was detected. Also,
When the silicon substrate was cut and the cross section of the thin film was observed with a SEM (scanning electron microscope), it was confirmed that crystals having a fine grain size were uniformly and densely distributed, and that a layered discontinuous surface due to stacking did not exist. Further, when a thin film sample was prepared and the piezoelectric body was observed by a TEM (transmission electron microscope), it was found that the thin film was composed of crystal grains having an average grain size of 0.03 μm.

An aluminum electrode is formed on the piezoelectric thin film obtained as described above by a vapor deposition method, and then polarized,
A piezoelectric thin film element was used. When the physical properties of the piezoelectric thin film element were measured, the relative dielectric constant was 2000 and the piezoelectric strain constant was 15
It showed excellent characteristics of 0 pC / N.

When the PZT thin film was dissolved in hydrofluoric acid and quantified by ICP (plasma emission analysis), the molar ratio of the composition was P.
b: Mg: Nb: Zr: Ti = 1.00: 0.05:
The ratio was 0.10: 0.45: 0.40, and although a slight decrease in lead was observed, other elements were the same as the raw material charging composition.

An ink jet recording head as shown in FIG. 3 was prepared using the piezoelectric thin film element obtained as described above. The sectional view which represents the concept when used is shown typically. A diaphragm of silicon nitride was formed on a silicon wafer by a sputtering method to form a lower electrode and a piezoelectric thin film.
The piezoelectric thin film was patterned by photoetching to have a width of 0.2 mm and a length of 4 mm, and a groove having a width of 0.3 mm was formed on the silicon wafer by anisotropic etching. After forming the gold upper electrode, it was joined to the second glass substrate to form the ink flow path 27. The substrate was cut to assemble an inkjet recording head. When ink was ejected using this head, sufficient ejection force was obtained. In addition, when printing was carried out by incorporating it in an ink jet recording apparatus, good printing quality was obtained.

[0086] Example A2~5 was prepared a coating solution in the same manner as in Example A1, except the molar ratio 0.067 and the molar ratio of niobium magnesium 0.1
33 was fixed, and 6 kinds of coating solutions were prepared by changing the molar ratio of zirconium and titanium as shown in Table 1 below. As polyethylene glycol, polyethylene glycol # 300 (Kanto Chemical Co., Inc., average molecular weight 285
~ 315) was used. After applying this sol on the substrate electrode,
By calcination at 400 ° C., an amorphous porous gel thin film with a thickness of 0.3 μm was formed. Further sol application and 400
Preliminary baking at 0 ° C. was repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Next, this thin film was rapidly heated to 650 ° C. and pre-annealed for 1 minute in an oxygen atmosphere using an RTA furnace. As a result, a crystalline dense film having a thickness of 0.6 μm was obtained. The above operation was repeated 10 times (that is, the coating liquid was applied 30 times).
Using an RTA furnace, it was annealed by holding it at 850 ° C. for 1 minute in an oxygen atmosphere. As a result, a piezoelectric thin film having a thickness of 6 μm was obtained. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element. The average crystal grain size and piezoelectric strain constant of this piezoelectric thin film element were as shown in the following table. No cracking was observed in any of the samples. In addition, there was no layered discontinuous surface due to lamination in the cross section.

[0087]

[Table 1]

Examples A6 to 9 A coating solution was prepared in the same manner as in Example A1, except that the molar ratio of magnesium was 0.033 and the molar ratio of niobium was 0.0.
67 was fixed and six types of coating solutions were prepared by varying the molar ratio of zirconium and titanium as shown in Table 2 below.
After coating the sol on the substrate electrode, the step of calcination at 400 ° C. was repeated three times to form an amorphous porous gel thin film with a thickness of 0.9 μm. Next, this thin film was pre-annealed at 550 ° C. for 10 minutes in an oxygen atmosphere using a diffusion furnace. As a result, a crystalline dense film having a thickness of 0.6 μm was obtained. The above operation was repeated 15 times (that is, the coating liquid was applied 45 times). Using an RTA furnace, it was annealed by holding it at 950 ° C. for 1 minute in an oxygen atmosphere. As a result, a piezoelectric thin film having a thickness of 9 μm was obtained.
An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element. The average crystal grain size and piezoelectric strain constant of this piezoelectric thin film element were as shown in the following table. No cracking was observed in any of the samples. In addition, there was no layered discontinuous surface due to lamination in the cross section.

[0089]

[Table 2]

Examples A10 to 14 A coating solution was prepared in the same manner as in Example A1, except that the molar ratio of zirconium and titanium was fixed at 1: 1 and magnesium and niobium were added as shown in Table 3. Seven types of coating solutions were prepared by changing the molar ratio. Here, the molar ratio of magnesium and niobium was fixed at 1: 2. After coating this sol on the substrate electrode, it was calcined at 350 ° C. to form an amorphous porous gel thin film. This thin film is then 550
Pre-annealing at 1 ° C. for 1 hour provided a crystalline dense film. The above operation was repeated 4 times to obtain a thin film, which was annealed at 850 ° C. for 20 minutes while flowing oxygen in the diffusion furnace. As a result, a piezoelectric thin film having a thickness of 2 μm was obtained. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and polarized to obtain a piezoelectric thin film element. The average crystal grain size and piezoelectric strain constant of this piezoelectric thin film element were as shown in the following table.

No cracking was observed in any of the samples. In addition, there was no layered discontinuous surface due to lamination in the cross section.

[0092]

[Table 3]

Example A15 An amorphous layer of metal oxide having the same composition as that of Example A1 was formed on the substrate electrode by sputtering to have a film thickness of 5 μm.
As a metal oxide sputter target, the metal molar ratio of the formed thin film was Pb: Mg: Nb: Zr: Ti = 1.0.
What was manufactured so that it might become 0: 0.05: 0.10: 0.45: 0.40 was used. The formed substrate was annealed by holding it at 900 ° C. for 1 minute in an oxygen atmosphere using an RTA furnace. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element. The average grain size of the crystal grains of the obtained piezoelectric thin film element is 0.
It was 05 μm. The dielectric constant was 1800, and the piezoelectric strain constant was 140 pC / N, showing excellent piezoelectric thin film element characteristics.

When an ink jet head using this piezoelectric thin film element was assembled and ink was ejected in the same manner as in Example A1, sufficient ejection force was obtained. When printing was performed by incorporating the ink jet recording apparatus in an ink jet recording apparatus, good printing quality was obtained.

Comparative Example A7 A piezoelectric thin film element was obtained in the same manner as in Example A1 except that annealing was performed at 750 ° C. in an RTA furnace. The average grain size of the crystal grains of this piezoelectric thin film element was less than 0.005 μm and could not be quantified. Further, the relative permittivity remained at 800 and the piezoelectric strain constant was 40 pC / N.

Comparative Example A8 A piezoelectric thin film element was obtained in the same manner as in Example A1 except that annealing was carried out at 1100 ° C. in an RTA furnace. The lead component of this piezoelectric thin film element was insufficient by about 20% as compared with Example A1. The average grain size of the crystal grains is 0.5 μm.
The relative dielectric constant is 800, and the piezoelectric strain constant is 20 p.
It was C / N.

Comparative Example A9 The same coating solution as in Example A1 was applied onto the same substrate as in Example A1. By calcining this substrate at 400 ° C,
An amorphous porous gel thin film was formed. Next, an RTA furnace was used for annealing at 900 ° C. for 1 minute in an oxygen atmosphere to obtain a piezoelectric thin film having a thickness of 0.2 μm. The above annealing process was repeated 6 times to obtain a piezoelectric thin film having a thickness of 1.2 μm. No cracks occurred in the thin film. A piezoelectric thin film element was prepared in the same manner as in Example A1. This piezoelectric thin film was composed of crystal grains with an average grain size of 0.05 μm, but the relative dielectric constant was 1200 and the piezoelectric strain constant was 60 pC /
It was N. When the cross section is observed by SEM, it is 0.2
There were layered discontinuities at μm intervals. It was difficult to perform photoetching on the thin film in this state.

The lead concentration in the thin film was lower than that in Example A1, and the lead concentration distribution was generated in the thickness direction of the film, and the thin film had a different sol composition.

Example B1 0.105 mol of lead acetate, 0.045 mol of zirconium acetylacetonate and 0.005 of magnesium acetate
Mol and were dissolved in 30 ml of acetic acid by heating to 100 ° C. After cooling to room temperature, 0.040 mol of titanium tetraisopropoxide and 0.010 of pentaethoxyniobium
Mol and were added to and dissolved in 50 ml of ethyl cellosolve. After stabilizing by adding 30 ml of acetylacetone, polypropylene glycol (average molecular weight 400) was added at a ratio of 30% by weight to the metal oxide in the sol,
Stir well to form a homogeneous sol.

A platinum electrode was formed on a silicon substrate by sputtering, and the sol was applied thereon by spin coating.
It was calcined at 00 ° C. As a result, an amorphous porous gel thin film having a thickness of 0.3 μm could be formed without cracks. Further, application of sol and calcination at 400 ° C. were repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Next, this substrate was subjected to an RTA furnace in an oxygen atmosphere for 5
Pre-annealing was performed by heating to 650 ° C. for 2 seconds and holding for 1 minute. As a result, a dense thin film having a thickness of 0.6 μm was obtained. When the thin film was examined by X-ray analysis, a pyrochlore type crystal peak was detected. Further, when examined by reflection type FT-IR (Fourier transform infrared absorption spectrum analysis), no absorption due to a methylene group near 2900 cm ^-1 was detected.

The step of applying the above-prepared sol to the thin film thus obtained by spin coating and pre-baking at 400 ° C. was repeated three times to obtain an amorphous porous gel having a thickness of 0.9 μm. A thin laminated film was obtained. Next, it was pre-annealed by holding it at 650 ° C. for 1 minute using an RTA furnace to obtain a crystalline dense film having a thickness of 1.2 μm.

The obtained substrate was patterned using a photoresist and etched with borofluoric acid. After removing the resist, the substrate was annealed by holding it at 900 ° C. for 1 minute in an oxygen atmosphere using an RTA furnace. 1.2
A piezoelectric thin film having a thickness equal to the μm thickness was obtained. When the piezoelectric thin film was examined by X-ray analysis, a sharp and strong peak of perovskite type crystal was detected. When the silicon substrate was cut and the cross section of the thin film was observed with a SEM (scanning electron microscope), it was confirmed that crystals having a fine grain size were uniformly and densely distributed, and that a layered discontinuous surface due to stacking did not exist. Further, when a thin film sample was prepared and the piezoelectric body was observed by a TEM (transmission electron microscope), it was found that the thin film was composed of crystal grains having an average grain size of 0.03 μm. Furthermore, no cracks were generated at all.

An aluminum electrode was formed on the piezoelectric thin film obtained as described above by a vapor deposition method and then polarized to obtain a piezoelectric thin film element. When the physical properties of this element were measured, the relative dielectric constant was 2000 and the piezoelectric strain constant was 150 pC / N.
And showed excellent characteristics.

When the PZT thin film was dissolved in hydrofluoric acid and quantified by ICP (plasma emission analysis), the molar ratio of the composition was P.
b: Mg: Nb: Zr: Ti = 1.00: 0.05:
The ratio was 0.10: 0.45: 0.40, and although a slight decrease in lead was observed, other elements were the same as the raw material charging composition.

An ink jet recording head using the piezoelectric thin film element thus obtained was prepared by the same method as in Example A1.

When ink was ejected from this ink jet recording head, a sufficient ejection force was obtained. Also, when incorporated into an inkjet recording device and printed,
Good print quality was obtained.

Example B2 A coating solution was prepared in the same manner as in Example B1, except that the molar ratio of magnesium was 0.067 and the molar ratio of niobium was 0.1.
33, the molar ratio of zirconium was 0.45, and the molar ratio of titanium was 0.35, and polypropylene glycol (average molecular weight 750) was added to the metal oxide in the sol at 3
0% by weight was added. After applying this sol to the substrate electrode, 4
By calcination at 00 ° C., an amorphous porous gel thin film with a thickness of 0.3 μm was formed. Further sol coating and 400 ℃
The pre-baking was repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Next, this thin film was rapidly heated to 650 ° C. in an oxygen atmosphere using an RTA furnace and pre-annealed for 1 minute. As a result, a crystalline dense film having a thickness of 0.6 μm was obtained. The above operation was repeated 10 times (that is, the number of times of application was 30 times). It was annealed by holding it at 850 ° C. for 1 minute in an oxygen atmosphere using an RTA furnace. As a result, a piezoelectric thin film having a thickness of 6 μm was obtained. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element.

The average crystal grain size of this piezoelectric thin film is 0.03.
μm, and the piezoelectric strain constant of this element is 150 p
It was C / N. In addition, no crack was observed. Furthermore, there was no layered discontinuous surface due to lamination in the cross section.

Example B3 A coating solution was prepared in the same manner as in Example B1, except that the molar ratio of magnesium was 0.033 and the molar ratio of niobium was 0.0.
67, the molar ratio of zirconium was 0.5, the molar ratio of titanium was 0.4, and polypropylene glycol (average molecular weight 400) was added in an amount of 20% by weight based on the metal oxide in the sol. After applying this sol on the substrate electrode, 400
The film thickness is 0.9 by repeating the process of calcination at 3 ℃.
A μm amorphous porous gel thin film was formed. Next, this thin film was pre-annealed at 550 ° C. for 10 minutes in an oxygen atmosphere using a diffusion furnace to obtain a crystalline dense film having a thickness of 0.6 μm. The above operation was repeated 15 times (that is, the number of times of application was 45 times). It was annealed by holding it at 950 ° C. for 1 minute in an oxygen atmosphere using an RTA furnace. As a result, a piezoelectric thin film having a thickness of 12 μm was obtained. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element.

The average crystal grain size of this piezoelectric thin film is 0.08.
μm, and the piezoelectric strain constant of this element is 170 p
It was C / N. In addition, no crack was observed. Furthermore, there was no layered discontinuous surface due to lamination in the cross section.

Example B4 A coating solution was prepared in the same manner as in Example B1, except that the molar ratio of magnesium was 0.04 and the molar ratio of niobium was 0.0.
8. The molar ratio of zirconium was 0.22, the molar ratio of titanium was 0.22, and 40% by weight of polypropylene glycol (average molecular weight 400) was added to the metal oxide in the sol. After applying this sol on the substrate electrode,
By calcination at 0 ° C., an amorphous porous gel thin film was formed. Next, this thin film was pre-annealed at 550 ° C. for 1 hour to obtain a crystalline dense film. The above operation was repeated 40 times. The obtained substrate was annealed at 850 ° C. for 20 minutes while flowing oxygen into the diffusion furnace. As a result, a 20 μm-thick piezoelectric thin film was obtained. An aluminum electrode was formed on the obtained piezoelectric thin film by vapor deposition and then polarized to obtain a piezoelectric thin film element.

The average crystal grain size of this piezoelectric thin film is 0.03.
μm, and the piezoelectric strain constant of this element is 120 p
It was C / N. In addition, no crack was observed. Furthermore, there was no layered discontinuous surface due to lamination in the cross section.

Example C1 Lead acetate (0.105 mol), zirconium acetylacetonate (0.045 mol), and magnesium acetate (0.005)
Mol and were dissolved in 30 ml of acetic acid by heating to 100 ° C. After cooling to room temperature, 0.040 mol of titanium tetraisopropoxide and 0.010 of pentaethoxyniobium
Mol and were added to and dissolved in 50 ml of ethyl cellosolve. After 30 ml of acetylacetone was added for stabilization, 30% by weight of polyethylene glycol # 400 (Kanto Chemical Co., Inc. reagent average molecular weight 380-420) was added to the metal oxide in the sol, and the mixture was stirred well to obtain a homogeneous sol. And

A platinum electrode was formed on a silicon substrate by a sputtering method, and the sol was applied thereon by spin coating.
It was calcined at 00 ° C. As a result, an amorphous porous gel thin film having a thickness of 0.3 μm could be formed without cracks. Further, application of sol and calcination at 400 ° C. were repeated twice to form a porous gel thin film having a thickness of 0.9 μm.
Next, this thin film was heated to 500 ° C. for 5 seconds and held for 5 minutes in an oxygen atmosphere using an RTA furnace, and further heated to 700 ° C. and held for 1 minute to perform pre-annealing. As a result, a dense thin film having a film thickness of 0.6 μm was obtained. When the thin film was examined by X-ray analysis, a pyrochlore type crystal peak was detected. Moreover, when it was examined by a reflection type FT-IR (Fourier transform infrared absorption spectrum analysis), 2
No absorption due to the methylene group near 900 cm ^-1 was detected.

The step of applying the sol prepared above by spin coating to the thin film thus obtained and pre-baking at 400 ° C. was repeated three times to obtain an amorphous porous gel having a thickness of 0.9 μm. A thin laminated film was obtained. Next, using an RTA furnace, pre-annealing was performed by holding at 500 ° C. for 5 minutes and further at 700 ° C. for 1 minute. As a result, a dense crystalline thin film having a thickness of 1.2 μm was obtained. The obtained substrate was patterned using a photoresist and etched with borofluoric acid. After removing the resist, the substrate was annealed by using an RTA furnace in an oxygen atmosphere at 600 ° C. for 5 minutes and further at 900 ° C. for 1 minute. As a result, a piezoelectric thin film having a thickness of 1.2 μm and a uniform thickness was obtained. When the thin film was examined by X-ray analysis, a sharp and strong peak of perovskite type crystal was detected. Cut the substrate, SEM
The cross section of the thin film was observed with a (scanning electron microscope), and it was confirmed that the crystals having a fine grain size were homogeneously and densely distributed, and that there was no layered discontinuous surface due to lamination. Further, when the thin film was observed with a TEM (transmission electron microscope), it was found that the thin film was composed of crystal grains having an average grain size of 0.03 μm. Furthermore, no cracks were observed at all.

An aluminum electrode was formed on the piezoelectric thin film obtained as described above by a vapor deposition method and then polarized to obtain a piezoelectric thin film element. When the physical properties of the piezoelectric thin film element were measured, the relative dielectric constant was 2000 and the piezoelectric strain constant was 160.
It showed excellent characteristics with pC / N.

When the PZT thin film was dissolved in hydrofluoric acid and quantified by ICP (plasma emission spectrometry), the molar ratio of the composition was P.
b: Mg: Nb: Zr: Ti = 1.00: 0.05:
The ratio was 0.10: 0.45: 0.40, and although a slight decrease in lead was observed, other elements were the same as the raw material charging composition.

An ink jet recording head using the piezoelectric thin film element thus obtained was prepared by the same method as in Example A1. When ink was ejected from this inkjet recording head, sufficient ejection force was obtained. In addition, when incorporated into an inkjet recording device and printed, good printing quality was obtained.

Example C2 A coating solution was prepared in the same manner as in Example C1, except that the molar ratio of magnesium was 0.067 and the molar ratio of niobium was 0.1.
33, the molar ratio of zirconium was 0.45, and the molar ratio of titanium was 0.35.
00 (Kanto Chemical Co., Inc. reagent average molecular weight 285 to 315)
Was added at a ratio of 30% by weight with respect to the metal oxide in the sol. After coating this sol on the substrate electrode, it was calcined at 400 ° C. to form an amorphous porous gel thin film with a thickness of 0.3 μm. In addition, apply sol and calcination at 400 ℃ 2
Repeated times to form a porous gel thin film having a thickness of 0.9 μm. Next, this thin film was rapidly heated to 600 ° C. in an oxygen atmosphere using an RTA furnace and held for 5 minutes.
Pre-annealing was performed by heating to 25 ° C. and holding for 1 minute. As a result, a crystalline dense film having a thickness of 0.6 μm was obtained. The above operation was repeated 10 times (that is, the number of times of coating was 30 times). Annealing was performed by using an RTA furnace in an oxygen atmosphere at 650 ° C. for 5 minutes and then at 900 ° C. for 1 minute. As a result, a piezoelectric thin film having a thickness of 6 μm was obtained. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element.

The average crystal grain size of this piezoelectric thin film is 0.03.
μm, and the piezoelectric strain constant of this element is 165 p
It was C / N. In addition, no crack was observed. Furthermore, there was no layered discontinuous surface due to lamination in the cross section.

Example C3 A coating solution was prepared in the same manner as in Example C1, except that the molar ratio of magnesium was 0.033 and the molar ratio of niobium was 0.0.
67, zirconium molar ratio 0.5, titanium molar ratio 0.4, and polyethylene glycol # 400
(Kanto Chemical Co., Inc. reagent average molecular weight 380 to 420) was added at a ratio of 20% by weight to the metal oxide in the sol. After coating the sol on the substrate electrode, the step of calcination at 400 ° C. was repeated three times to form an amorphous porous gel thin film with a thickness of 0.9 μm. Next, this thin film was heated to 500 ° C. and held for 5 minutes in an oxygen atmosphere using a diffusion furnace, and further heated to 650 ° C. and held for 10 minutes for pre-annealing. As a result, a dense crystalline thin film having a thickness of 0.6 μm was obtained. The above operation was repeated 15 times (that is, the number of times of coating was 45 times). Annealing was performed by using an RTA furnace in an oxygen atmosphere at 700 ° C. for 5 minutes and further at 950 ° C. for 1 minute. As a result, thickness 12
A piezoelectric thin film of μm was obtained. An aluminum electrode is formed on the obtained piezoelectric thin film by vapor deposition, and then polarized,
A piezoelectric thin film element was used.

The average crystal grain size of this piezoelectric thin film is 0.08.
μm, and the piezoelectric strain constant of this element is 170 p
It was C / N. In addition, no crack was observed. Furthermore, there was no layered discontinuous surface due to lamination in the cross section.

Example D1 0.110 mol of lead acetate (10 mol% excess of lead component),
Zirconium acetylacetonate 0.045 mol,
0.005 mol of magnesium acetate was dissolved in 30 ml of acetic acid by heating at 100 ° C. Cool to room temperature,
0.040 mol of titanium tetraisopropoxide and 0.010 mol of pentaethoxyniobium were added and dissolved in 50 ml of ethyl cellosolve. 30 acetylacetone
After stabilizing by adding ml, polyethylene glycol # 400 (Kanto Chemical Co., Inc. reagent average molecular weight 380-42
0) was added at a ratio of 30% by weight with respect to the metal oxide in the sol and stirred well to form a homogeneous sol.

A platinum electrode was formed on a silicon substrate by a sputtering method, and the sol was applied thereon by spin coating.
It was calcined at 00 ° C. As a result, an amorphous porous gel thin film having a thickness of 0.3 μm could be formed without cracks. Further, application of sol and calcination at 400 ° C. were repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Then, using an RTA furnace in an oxygen atmosphere for 65 seconds, 65
Pre-annealing was performed by heating to 0 ° C. and holding for 1 minute.
As a result, a dense thin film having a thickness of 0.6 μm was obtained.
When the thin film was examined by X-ray analysis, a pyrochlore type crystal peak was detected. In addition, reflective FT-IR
When examined by (Fourier transform infrared absorption spectrum analysis), no absorption due to a methylene group near 2900 cm ^-1 was detected.

The process of applying the sol prepared above to the thin film thus obtained by spin coating and pre-baking at 400 ° C. was repeated three times to obtain an amorphous porous gel having a thickness of 0.9 μm. A thin laminated film was obtained. Next, it was pre-annealed by holding it at 650 ° C. for 1 minute using an RTA furnace to obtain a crystalline dense film having a thickness of 1.2 μm. The obtained substrate was patterned using a photoresist and etched with borofluoric acid. After removing the resist, the substrate was annealed by holding it at 900 ° C. for 1 minute in an oxygen atmosphere using an RTA furnace. A piezoelectric thin film having the same thickness of 1.2 μm was obtained. When the piezoelectric thin film was examined by X-ray analysis, a sharp and strong peak of perovskite type crystal was detected. In addition, when the silicon substrate was cut and the thin film cross section was observed with a SEM (scanning electron microscope), it was confirmed that crystals with a minute grain size were uniformly and densely distributed and that a layered discontinuous surface due to stacking did not exist. .
In addition, a thin film sample is prepared and TEM (transmission electron microscope)
By observing the piezoelectric body, the average particle diameter was 0.06μ.
It was found that the thin film was composed of m crystal grains.
Furthermore, no cracks were generated at all.

Aluminum electrodes were formed on the piezoelectric thin film obtained as described above by a vapor deposition method and then polarized to obtain a piezoelectric thin film element. When the physical properties of this element were measured, the relative dielectric constant was 2300 and the piezoelectric strain constant was 170 pC / N.
And showed excellent characteristics.

When the PZT thin film was dissolved in hydrofluoric acid and quantified by ICP (plasma emission analysis), the molar ratio of the composition was P.
b: Mg: Nb: Zr: Ti = 1.04: 0.05:
The ratio was 0.10: 0.45: 0.40, and although a slight decrease in lead was observed, other elements were the same as the raw material charging composition.

An ink jet recording head using the piezoelectric thin film element obtained as described above was manufactured by the same method as in Example A1. When ink was ejected from this inkjet recording head, sufficient ejection force was obtained. In addition, when incorporated into an inkjet recording device and printed, good printing quality was obtained.

Example D2 A coating solution was prepared in the same manner as in Example D1, except that
With a lead component in an excess of 15 mol%, the molar ratio of magnesium is 0.067, the molar ratio of niobium is 0.133, the molar ratio of zirconium is 0.45, and the molar ratio of titanium is 0.35. 300 (Kanto Chemical Co., Inc. reagent average molecular weight 285 to 315) was added at a ratio of 30% by weight to the metal oxide in the sol. After coating this sol on the substrate electrode, it was calcined at 400 ° C. to form an amorphous porous gel thin film with a thickness of 0.3 μm. Further, sol application and calcination at 400 ° C. are repeated twice, and
A porous gel thin film having a thickness of 9 μm was formed. Next, this thin film was rapidly heated to 650 ° C. in an oxygen atmosphere using an RTA furnace and pre-annealed for 1 minute. As a result, 0.6μ
An m-thick crystalline dense film was obtained. Further operation 1
It was repeated 0 times (that is, the number of times of application was 30 times). As a result, a piezoelectric thin film having a thickness of 6 μm was obtained.
It was annealed by holding it in an oxygen atmosphere at 850 ° C. for 1 minute using an RTA furnace. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element.

The average crystal grain size of this piezoelectric thin film is 0.05.
μm, the relative permittivity of this device was 2400, and the piezoelectric strain constant was 175 pC / N. No crack was observed. Furthermore, there was no layered discontinuous surface due to lamination in the cross section.

Example D3 A coating solution was prepared in the same manner as in Example D1, except that
With a lead component in an excess of 20 mol%, the molar ratio of magnesium is 0.033, the molar ratio of niobium is 0.067, the molar ratio of zirconium is 0.5, and the molar ratio of titanium is 0.4.
Further, polyethylene glycol # 400 (reagent average molecular weight of 380 to 420 manufactured by Kanto Chemical Co., Inc.) was added at a ratio of 20% by weight to the metal oxide in the sol. After coating the sol on the substrate electrode, the step of calcination at 400 ° C. was repeated three times to form an amorphous porous gel thin film with a thickness of 0.9 μm. Next, this thin film was pre-annealed at 550 ° C. for 10 minutes in an oxygen atmosphere using a diffusion furnace. As a result, a dense crystalline thin film having a thickness of 0.6 μm was obtained. The above operation was repeated 15 times (that is, the number of times of application was 4
It was 5 times). As a result, a piezoelectric thin film having a thickness of 12 μm was obtained. It was annealed by holding it in an oxygen atmosphere at 950 ° C. for 1 minute using an RTA furnace. An aluminum electrode is formed on the obtained piezoelectric thin film by vapor deposition, and then polarized,
A piezoelectric thin film element was used.

The average crystal grain size of this piezoelectric thin film is 0.08.
μm, the relative permittivity of this element was 2300, and the piezoelectric strain constant was 185 pC / N. In addition, no crack was observed. Furthermore, there was no layered discontinuous surface due to lamination in the cross section.

Inkjet recording heads using the piezoelectric thin film elements of Examples D2 and D3 were manufactured in the same manner as in Example A1. When ink was ejected using this head, sufficient ejection force was obtained. When printing was performed by incorporating the ink jet recording apparatus in an ink jet recording apparatus, good printing quality was obtained.

Example E1 0.002 mol of bismuth acetate, 0.103 mol of lead acetate, 0.045 mol of zirconium acetylacetonate and 0.005 mol of magnesium acetate were added to 30 ml of acetic acid and heated to 100 ° C. Dissolved. After cooling to room temperature, 0.040 mol of titanium tetraisopropoxide,
0.010 mol of pentaethoxyniobium was dissolved in 50 ml of ethyl cellosolve and added. After stabilizing by adding 30 ml of acetylacetone, polyethylene glycol was added at a ratio of 30% by weight with respect to the metal oxide in the sol, and well stirred to obtain a homogeneous sol.

A platinum electrode was formed on a silicon substrate by a sputtering method, and the sol was applied thereon by spin coating.
It was calcined at 00 ° C. As a result, an amorphous porous gel thin film having a thickness of 0.3 μm could be formed without cracks. Further, application of sol and calcination at 400 ° C. were repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Next, this thin film was placed in an oxygen atmosphere using an RTA furnace for 5
Pre-annealing was performed by heating to 650 ° C. for 2 seconds and holding for 1 minute. As a result, a dense thin film having a thickness of 0.6 μm was obtained. When this thin film was examined by X-ray analysis, a pyrochlore type crystal peak was detected. Further, when examined by a reflection type FT-IR, absorption due to a hydroxyl group around 3400 cm ^-1 was not detected.

The step of applying the sol prepared above to the thin film thus obtained by spin coating and pre-baking at 400 ° C. was repeated three times to obtain an amorphous porous gel having a thickness of 0.9 μm. A thin laminated film was obtained. Next, this laminated film was pre-annealed by holding it at 650 ° C. for 1 minute using an RTA furnace to obtain a crystalline dense film having a thickness of 1.2 μm.

The obtained thin film was patterned using a photoresist and etched with borofluoric acid. After removing the resist, the substrate was annealed by holding it at 900 ° C. for 1 minute in an oxygen atmosphere using an RTA furnace. 1.2
A piezoelectric thin film having a thickness equal to the μm thickness was obtained. When the piezoelectric thin film was examined by X-ray analysis, a sharp and strong peak of perovskite type crystal was detected. Also,
When the silicon substrate was cut and the cross-section of the thin film was observed by SEM (scanning electron microscope), it was confirmed that crystals having a fine grain size were uniformly and densely distributed, and that a layered discontinuous surface due to stacking did not exist. In addition, a thin film sample is prepared and TEM
Observation of the piezoelectric body with a (transmission electron microscope) revealed that the thin film was composed of crystal grains having an average grain size of 0.03 μm. ICP by dissolving PZT thin film with hydrofluoric acid
Quantitatively determined by (plasma emission analysis), the molar ratio was P
b: Bi: Mg: Nb: Zr: Ti = 0.98: 0.0
2: 0.05: 0.10: 0.45: 0.40,
Although a slight decrease in lead was observed, the composition of other elements was the same as the raw material charge composition.

The composition of the PZT thin film (piezoelectric thin film) obtained in this example is (Pb + Bi): Mg: Nb:
Rewriting as Zr: Ti, 1.00: 0.05: 0.1
The ratio was 0: 0.45: 0.40, which is the same composition ratio as in Example A1. That is, the composition of the piezoelectric thin film of Example E1 had a structure in which 2% of Pb in Example A1 was replaced with Bi. An aluminum electrode was formed on the obtained piezoelectric thin film by a vapor deposition method and then polarized to obtain a piezoelectric thin film element. When the physical properties of this element were measured, the relative dielectric constant was 100.
0, the piezoelectric strain constant showed a characteristic of 120 pC / N.

Comparing the characteristics of the piezoelectric thin film according to this example with those of Example A1, the relative dielectric constant is 50% lower and the piezoelectric strain constant is 20% lower. However, the piezoelectric thin film of this example was extremely advantageous from the viewpoint of heat generation in an inkjet recording head in which the piezoelectric thin film element occupies a large area.

An ink jet recording head was prepared using the piezoelectric thin film element obtained as described above. The sizes of the piezoelectric thin film and the ink flow path were the same as in Example A1. The applied voltage was increased by 20% in order to compensate for the shortage of piezoelectric strain characteristics of the piezoelectric thin film. As a result, the amount of heat generated when the piezoelectric thin film was driven could be reduced by 75% without impairing the flight characteristics of the ink. In addition, the volume of the ink flow path was increased for the purpose of increasing the amount of ejected ink droplets. Specifically, the width of the ink flow path is changed from 0.3 mm to 0.4 mm, and the width of the piezoelectric thin film is changed from 0.2 mm to 0.3 mm.
mm. Although the area of the piezoelectric thin film, that is, the capacitor increased by 50%, the capacitance of the capacitor decreased by 25% because the relative dielectric constant was small, and the amount of heat generation could be suppressed.

Example E2 As a raw material for the sol, 0.005 mol of lanthanum acetate, 0.998 mol of lead acetate, 0.045 mol of zirconium acetylacetonate, 0.005 mol of magnesium acetate and 0.040 mol of titanium tetraisopropoxide. Example E1 except that 0.010 mol of pentaethoxyniobium was used.
A piezoelectric thin film was formed in the same manner as in.

The composition of the obtained piezoelectric thin film was Pb: L.
a: Mg: Nb: Zr: Ti = 0.95: 0.05:
0.05: 0.10: 0.45: 0.40, and (P
b + La): Mg: Nb: Zr: Ti.
It became 00: 0.05: 0.10: 0.45: 0.40. That is, 5% of Pb in the piezoelectric thin film of Example A1 was replaced with La. When the piezoelectric characteristics of the obtained piezoelectric thin film were measured after polarization, the relative dielectric constant was 25.
00, the piezoelectric strain constant was 140 pC / N. The Young's modulus Y of the piezoelectric thin film was 5 × 10 ¹⁰ Pa, and Example A1
The piezoelectric film had a softer film quality as compared with Young's modulus Y = 6 × 10 ¹⁰ Pa.

Examples E3 to 15 The piezoelectric thin film has a chemical formula of xPb (Mg _1/3 Nb _2/3 ) O ₃
-YPbZrO ₃ -zPbTiO ₃ (x, y, z represents a molar ratio, x + y + z = 1) In a piezoelectric material, a part of Pb, Zr, Ti, Nb, a part of Mg in this chemical formula, or all of Mg A piezoelectric thin film in which was replaced with another element was prepared in the same manner as in Example E2.

Table 4 shows the relative permittivity and Young's modulus of the piezoelectric thin film in which Pb was replaced with Sr, Ca, or Ba. As the raw material of the sol, Sr was diethoxystrontium and Ca and Ba were acetates.

The dielectric constant and Young's modulus of the piezoelectric thin film in which Zr and Ti were replaced with Sb, Fe, Al or Cr were as shown in Table 5. As the raw material of the sol, triethoxyantimony was used for Sb, and acetates were used for Fe, Al, and Cr, respectively.

Table 6 shows the relative dielectric constant and Young's modulus of the piezoelectric thin film in which Mg was replaced with Co, Zn, Mn, or Ni. Acetate was used as the raw material of the sol.

Table 7 shows the relative dielectric constant and Young's modulus of the piezoelectric thin film in which Nb was replaced with Ta or Sb. In addition, triethoxy antimony or pentamethoxy tantalum was used as a raw material of the sol.

[0148]

[Table 4]

[0149]

[Table 5]

[0150]

[Table 6]

[0151]

[Table 7]

[Brief description of drawings]

FIG. 1 is a three-component composition diagram showing a preferable composition of a piezoelectric thin film according to the present invention.

FIG. 2 is a diagram schematically showing a method of manufacturing a piezoelectric thin film according to the first aspect of the present invention.

FIG. 3 is a diagram schematically showing a method of manufacturing a piezoelectric thin film according to the second aspect of the present invention.

FIG. 4 is a schematic diagram of an inkjet recording head using a piezoelectric thin film according to the present invention.

[Explanation of symbols]

11 substrate 12 electrode 13 porous gel thin film 14 crystalline dense thin film 15 piezoelectric thin film having large perovskite type crystal grains 21 silicon substrate 22 vibrating plate 23 lower electrode 24 piezoelectric thin film 25 upper electrode 26 second substrate 27 ink reservoir

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C04B 35/49 C04B 35/49 MH01L 21/316 H01L 41/08 C 41/09 41/22 A 41/24 (31) Priority claim number Japanese Patent Application No. 7-322659 (32) Priority Day No. 7 (1995) December 12 (33) Priority claiming country Japan (JP) (31) Priority claim No. Japanese Patent Application No. 7- 322660 (32) Priority Day 7 (1995) December 12 (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application 7-322661 (32) Priority Day 7 (1995) 12 12th (33) Priority claiming country Japan (JP) (72) Inventor Masami Murai 3-5 Yamato 3-chome, Suwa City, Nagano Seiko Epson Corporation (72) Inventor Satoshi Takahashi Nagano Prefecture Seiko Epson Co., Ltd. 3-3-5 Yamato, Suwa-shi

Claims (20)

[Claims] 1. A piezoelectric thin film having a thickness of 0.5 μm or more and 20 μm or less, wherein the thin film is composed of crystal grains having an average grain size of 0.005 μm or more and 0.2 μm or less, and has a layered discontinuity in the thin film cross section. A piezoelectric thin film that does not have a surface. 2. The thin film is xPb (Mg _1/3 Nb _2/3 ) O.
_{3 -yPbZrO 3 -zPbTiO 3} (here, x,
y and z represent a molar ratio, and x + y + z = 1), which is composed of a three-component system piezoelectric material and is represented by the following A, B, and A piezoelectric thin film having a composition within the range of four points C and D. A (x = 0.05, y = 0.40, z = 0.55) B (x = 0.05, y = 0.60, z = 0.35) C (x = 0.25, y = 0.30, z = 0.45) D (x = 0.25, y = 0.50, z = 0.25) 3. The piezoelectric thin film is Pb (1-α) Γα
[(Mg _1/3 Nb _2/3 ) xZryTiz] O ₃ (where x, y and z represent molar ratios, and x + y + z = 1), where x, y and z are three In the composition chart of the component system, the following four points A, B, C, and D are present: A (x = 0.05, y = 0.40, z = 0.55), B (x = 0.05, y = 0.60, z = 0.35), C (x = 0.25, y = 0.30, z = 0.45), D (x = 0.25, y = 0. 50, z = 0.25), and Γ in the above formula is Sr, Ca, Ba, Bi, or L
represents any element of a, and α in the above formula is 0 <α
A piezoelectric thin film, which is an arbitrary number that satisfies the relation of ≦ 0.2. 4. In the thin film, a part or all of Mg in the formula is Co, Zn, M.
substituted by an element selected from n and Ni,
And / or the thin film is a part of Nb in the formula,
4. The composition according to claim 2 or 3, having a composition in which Ta or Sb is substituted and / or a part of Zr or Ti in the formula is substituted by an element selected from Sb, Fe, Al and Cr. Piezoelectric thin film. 5. Pb: (Mg +
The piezoelectric thin film according to claim 2, further containing Nb + Zr + Ti) in a molar ratio range of 1 to 1.2: 1. 6. A piezoelectric thin film element, comprising the piezoelectric thin film according to claim 1 sandwiched between two electrode layers. 7. A method for producing a piezoelectric thin film according to claim 1, which is a sol-gel method, comprising: a) a sol of a metal component constituting the piezoelectric film, and a polymer compound. A step of applying a sol composition containing a sol composition onto a substrate and drying the sol composition to form a film; and b) baking the obtained film to form a porous gel containing an amorphous metal oxide. A calcination step of forming a thin film, c) a pre-annealing step of annealing the obtained porous gel thin film to form a film made of a crystalline metal oxide, and d) the above steps a) and b). , And c) are repeated at least once to form a laminated film of crystalline metal oxide, and e) the film obtained in step d) is annealed to form perovskite-type crystal grains in the film. A step of growing a large amount of. 8. A method for manufacturing a piezoelectric thin film according to claim 1, which is a sol-gel method, comprising: a) a sol of a metal component constituting the piezoelectric film, and a polymer compound. A step of applying a sol composition containing a sol composition onto a substrate and drying the sol composition to form a film; and b) baking the obtained film to form a porous gel containing an amorphous metal oxide. A calcination step of forming a thin film, f) a step of repeating the above steps a) and b) at least once to form a laminated film of porous thin films containing an amorphous metal oxide, and c ′. ) A pre-annealing step of annealing the laminated film to form a film made of a crystalline metal oxide, and d ′) the above steps f) and c ′) are repeated at least once, to obtain a crystalline metal. Obtained by the step of forming a laminated film of oxide films, and e ′) step d ′) And annealing the film, comprising a step of growing a large crystal grains of perovskite-type in the film, method. 9. The lead component in the sol is Pb: (M
9. The method for producing a piezoelectric thin film according to claim 7, wherein the excess is made in a molar ratio range of g + Nb + Zr + Ti) = 1 to 1.2: 1. 10. The method for producing a piezoelectric thin film according to claim 7, wherein the pre-annealing in step c) or c ′) is performed at a temperature in the range of 400 ° C. to 800 ° C. 11. The method for producing a piezoelectric thin film according to claim 7, wherein the annealing in step e) or e ′) is performed at a temperature in the range of 600 ° C. to 1200 ° C. 12. The method for producing a piezoelectric thin film according to claim 7, wherein the annealing in step e) or e ′) is performed at a temperature in the range of 800 ° C. to 1000 ° C. 13. The pre-annealing in the step c) or c ') is performed in two steps, and the first step is 400 times.
℃ ~ 600 ℃ temperature range, the second step is 600 ℃
The method for producing a piezoelectric thin film according to any one of claims 7 to 9, wherein the method is performed at a temperature in the range of ~ 800 ° C. 14. The annealing in the step e) or e ′) is performed in two steps, and the first step is performed at 600 ° C.
Perform at a temperature in the range of 800 ℃, the second step is 800 ℃
The method for producing a piezoelectric thin film according to any one of claims 7 to 9, which is performed at a temperature in the range of to 1000 ° C. 15. The film thickness of the porous thin film formed in the step b) or the film thickness of the porous thin film newly formed in the step f) is 0.01 μm or more and 1 μm or less. 10. The method for manufacturing a piezoelectric thin film according to any one of items 9 to 10. 16. A method of forming a laminated film of a film made of a crystalline metal oxide, obtained by the step d) or d ′), before the step e) or e ′). The method for manufacturing a piezoelectric thin film according to claim 7, comprising a step of patterning. 17. The method for producing a piezoelectric thin film according to claim 7, wherein the polymer compound added to the sol composition is polyethylene glycol. 18. The method for producing a piezoelectric thin film according to claim 7, wherein the polymer compound added to the sol composition is polypropylene glycol. 19. A thickness of 0.5 μm or more and 20 μm, which can be produced by the method according to claim 7. Description:
A piezoelectric thin film having an average particle size of 0.0 or less.
A piezoelectric thin film having a crystal grain size of from 05 μm to 0.2 μm and having a layered cross section. 20. An ink jet recording head, comprising the piezoelectric thin film according to claim 1 as a vibrator.